I'm running an experiment in gamma-ray imaging (although the main emission from the decay of Am-241 is ~60keV, so much more in the range of x-rays). I'm curious as to the sort of sources that would produce the background radiation the gamma-ray detector is seeing.

I'm less interested by the affect of this radiation on biology (i.e. in Sieverts) but rather what the detector is receiving (i.e. Curies or Becquerels) if that information is available.

Some sources might be cosmic rays or possibly radon decay?. What other sources would be prominent in this range?


  • $\begingroup$ I asked the same question recently but didn't explain myself very well so this is a complete rephrasing. $\endgroup$
    – buzsh
    Mar 27, 2015 at 12:15
  • 1
    $\begingroup$ A spectrum or a hint about what energies you are seeing in the detector, and some information about what kind of detector you are using would really help. There are several regular users here who have some experience with one or more classes of detectors, but the thing we all know is that there are a lot of possible answers. Give us something to work with here. $\endgroup$ Mar 27, 2015 at 13:57
  • $\begingroup$ Cosmic rays typically have energies > 10 MeV, though solar wind deflects most of them away from us until energies > 10 GeV. They could create secondaries that could be in the keV range, but I don't believe the production would be consistent (i.e., more periodic and not really a background). $\endgroup$
    – Kyle Kanos
    Mar 27, 2015 at 14:21
  • $\begingroup$ Using an Ortec germanium detector at about 3.75kV looking at what might be populating the background radiation in the 0-100 keV region. It looks like an exponential decay out from 0keV with two distinct doublets ~70-80keV that I'm fairly sure are the lead Ka and Kb from the lead castle the detector is in. Just curious what would be causing so many counts 0-40keV. Ta $\endgroup$
    – buzsh
    Mar 27, 2015 at 16:22
  • $\begingroup$ BTW, You should edit the data in that comment into the question. That makes the question self contained and does not ask every reading to parse the comment thread to figure out what is going on. Further, comments are transient and subject to deletion. $\endgroup$ Mar 27, 2015 at 17:31

1 Answer 1


All high bias detectors experience electronics noise which rises roughly exponentially toward low energy. Add to that the (single, double, ...) Compton edges from the lines you are trying to sample and you can expect a lot of background down there without needing there to be any actual x-rays flying around in those energies.

Most of the Ortec devices run Ortec' DAQ software which can capture spectra to a format that can be converted to an image. If you want an expert opinion you could post such an image, but a rising mess of stuff is par for the course at the low end of the devices energy sensitivity.


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